I can say that I put a nylon knee high full of kitty litter in my waterfall, and also planted all my lilies in kitty litter, and the algae has quit growing. It was growing so fast I was pulling it every other day! I will also add that I also put the Pond Perfect in the filter to run through the pond, and that may have done the trick as well. It's like adding beneficial bacteria to jump start the filter. I used it last 2 weekends, and plan to use it this weekend again at double dose, then back to normal dose and quit if it goes away. Oh, and I also have UV light on, but that doesn't help with string or carpet algae, just the suspended stuff, but I didn't want that this year either, so plugged it in for a month or so.